RFID material tracking method and apparatus

ABSTRACT

A method and apparatus for tracking items automatically is described. A passive RFID (Radio Frequency IDentification) tag is used with a material tracking system capable of real-time pinpoint location and identification of thousands of items in production and storage areas. Passive RFID tags are attached to the item to be tracked, remote sensing antennas are placed at each remote location to be monitored, interrogators with several antenna inputs are connected to the sensing antennas to multiplex the antenna signals, and a host computer communicates with the interrogators to determine item locations to an exacting measure.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a division of U.S. patent application Ser. No.09/371,717, filed on Aug. 9, 1999, now U.S. Pat. No. 6,714,121, thespecification of which is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates generally to radio frequencyidentification, and more specifically to a tracking system, method, andcomponents for use with radio frequency identification.

BACKGROUND OF THE INVENTION

Numerous systems exist for the physical tracking of inventory, rawmaterials, materials in manufacture, or other items in a variety oflocations, such as manufacturing facilities, libraries, offices, and thelike. Accurate and inexpensive locating, tracking, and inventorying ofthe physical location of items such as parts, goods, and materials is anecessity for many operations, such as manufacturing and warehousing,for a number of reasons. Such reasons include the desire or need toquickly determine the physical location of a part in the manufacturingprocess, or to determine whether a part is present in inventory orstorage, to determine the quantity of an item on hand, to track theprogress of an item in manufacture, and many other such functions.

Apparatuses and methods for the performance of the tracking of materialand the performance of inventory-like processes have evolved over time.For example, inventory strategies have been modified from the handtallying of stock and location in a notebook or the like, tosophisticated computer driven hardware and software for trackinginventory. Traditionally, a full inventory operation could close anentire facility, such as a retail store, warehouse, or manufacturingplant, for a day or more every time a detailed inventory was required.The large costs associated with physically shutting down an operation todo inventory were and are a known cost of the operation of manybusinesses.

An accurate record of the items available in a store or warehouse, aswell as their location, is a key component of successfully operating abusiness. Knowing what is on hand allows the skilled manager or supplypersonnel to make informed ordering decisions. Knowledge of theavailability and location of items or parts in a facility decreases theamount of time necessary for retrieval of such items, thereby increasingoverall efficiency.

The advent of computers, and their rapid entrenchment into mainstreambusinesses and personal life, has also led to an advent in trackingitems and performing and maintaining an inventory. For example, whenphysical inventory was still routinely performed by hand, a databasecould be created and maintained to track inventory in a more dynamicfashion. The potential errors of misplacing the physical inventorysheet, and the potential corruption of the physical inventory recordwere replaced with the increasingly lower incidence of potential errorsof lost data and data corruption. Data entry error still also posedpotential human error problems. Still, the computerized storage andretrieval of inventory information allowed for various sorting andcategorization of data not previously easily available. The databasefunctions of hand entered computer inventories were readily extended toother material tracking endeavors such as warehousing, stocking,ordering, and the like.

As technology continued to advance, various apparatuses and methods fortracking the inventory of a retail store, manufacturing plant,warehouse, and the like, in real-time or near real-time, were placedinto use. Production lot tracking technology systems had and have widelyvaried capability, success, ease of use, and cost. Currently proposedand available lot tracking technologies include manual keyboard entry,bar coding, and proprietary systems such as those provided by JENOPTIK,Fluoroware, Micron Communications, Inc., and Omron.

Manual keyboard entry of lot numbers of parts in a lot tracking orinventory situation is already in use in many facilities. Such systemsare not automated, but instead are manually performed. The physicalinventory process is still undertaken, and generally the informationgathered is entered into a computerized database. Data entry errors dueto human error are in large part an unavoidable part of the manualinventory process. Such errors are difficult if not impossible to trackand correct. Any information which is desired or required to be obtainedand stored or entered into a computer or other system beyond a simpleinventory creates additional work for the inventory taker. The time ittakes to perform an inventory using manual keyboard entry of lot numbersand the like is not significantly less than traditional pencil and paperinventories which often require the full or at least partial shutdown ofan entire facility. Such an inventory process is subject to high costsreflected not necessarily in terms of equipment, but in terms ofemployee-hours and lost revenues from a shutdown.

Because of its advantages over manual inventory, whether using acomputer for further organization or not, bar coding has becomecommonplace in many if not most retail outlets and warehouses, grocerystores, chains, and large retail outlets. In a bar coding scheme, anidentifying label containing encoded information is placed on the goods,parts, part bin, or other item to be identified by a bar code reader.The encoded information is read by the reader with no user data entrygenerally required. This is referred to as keyless data entry. Theinformation encoded on the bar code is then typically passed to acomputer or other processing medium for decoding and data entry. Suchdata entry is largely error free due to the decreased reliance onerror-prone human activities. Bar code data entry is also typicallyfaster than manual data entry.

Bar coding is a common and easy to implement technology. However, barcoding requires a scanner or reader for every terminal, or a portablescanner which is moved around from location to location. Further, barcoding requires a separate label for implementation. Without furtherdata entry, which has additional associated costs and potential errorfactors, other desired or required information such as an exact locationof the scanned item is unknown.

Another type of lot tracking system uses an infrared lot box microterminal with a pager-like display for lot tracking. A micro terminal isphysically attached to each lot box. Each micro terminal communicatesvia infrared communication with an infrared (IR) transceiver grid, whichmust be in sight of the micro terminal in order for the system tofunction properly. Typically, the IR transceiver grid is positioned orinstalled along the ceiling of a facility. Stacked pallets, lots, orwafer boats will be unreadable using an IR system. The micro terminalsand IR transceiver grid of the IR system are expensive. A micro terminalsystem requires an elaborate software platform, but does allow forreduced data entry error, faster data entry, and simple user entries.The IR system requires a major procedural change in the standards forperforming lot tracking. The micro terminals must also be positioned ina specific orientation with respect to the transceiver grid for properfunctioning. The terminal must be physically attached to a lot box to betracked. Lot location can only be identified to an area as small as theIR field of view.

Another lot tracking system is available from Fluoroware. This systemuses passive tags in a cassette. The passive tags are scanned by ascanning station over which an item, wafer boat, or lot which has beentagged passes. The item, lot, or boat is identified when it passes overthe scanning station. Often, wafer boats are specific to the particularstation, but parts may be moved to a number of different locations.Tracking a cassette may require a large amount of reassociation of thetag information to accurately track the part or item. The scanningstations of the Fluoroware system are expensive, on the order of$2,000-$3,000 per station. Additionally, a main computer to centralize,organize, and coordinate operation of the tracking system is required.The Fluoroware system, like other more automated systems, reduces dataentry error and data entry time. The tags used in the system arerelatively low in cost, and can be embedded into boats. However, manycontrollers are needed for the system, and the scanning stations have ahigh cost. Further, the reassociation of tags with different locationsrequires extra data entry or tag reprogramming, which introduces furtherpotential errors.

When an inventory or lot tracking system works with a large number ofparts or locations, which may number into the thousands of locations andmany thousands if not millions of parts, the systems described abovebecome unwieldy to effectively operate, become cost prohibitive, orboth. Further, with a large number of parts and locations, an exactlocation match is difficult if not impossible to provide with the abovesystems. Such a lack of ability to pinpoint the location of a partfurther hinders the operation and effectiveness of the above systems.

Additionally, items or lots in a manufacturing facility may sit in acertain location without being used or moved for weeks or more. Inaddition, the pallets of wafer boats in such a facility or storage areamay be stacked in stacks five or more layers deep. Personnel are oftenassigned to physically search all lots to find a lot which may bemissing. Lots in large manufacturing facilities have been known to belost for 6 months to a year. A more accurate tracking system for lotswould be desirable.

In manufacturing situations, other tracking of inventory and parts isoften desirable or necessary. Such other tracking may include trackingthe amount of time a part spends between stations, the amount of time ittakes for a part to complete a certain operation, a history of thetravel of a part from start to finish of a manufacturing or fabricationoperation, and the like.

SUMMARY OF THE INVENTION

The present invention solves the above-mentioned problems in the art andother problems which will be understood by those skilled in the art uponreading and understanding the present specification. The presentinvention provides a method and apparatus for tracking itemsautomatically. An apparatus embodiment of the present invention is apassive RFID (Radio Frequency IDentification) tag material trackingsystem capable of real-time pinpoint location and identification ofthousands of items in production and storage areas. Passive RFID tagsare attached to the item to be tracked, remote sensing antennas areplaced at each remote location to be monitored, scanning interrogatorswith several multiplexed antenna inputs are connected to the sensingantennas, and a host computer communicates with the interrogators todetermine item locations to an exacting antenna position.

Another embodiment of the present invention is a method for tracking thelocation of an object having an identification tag attached to or nearthe object, using an interrogator connected to a sensing antenna and toa computer, comprising activating the sensing antenna, determining ifthere is a voltage at the sensing antenna, obtaining data from a passiveidentification tag attached to the object, and communicating between thehost computer and the interrogator to log tag location data.

Still another embodiment of the present invention is an RFID materialtracking system, comprising a plurality of RFID tags, each tagattachable to a container or an item to be tracked, a plurality ofsensing antennas, each antenna placeable at a location to be monitored,a plurality of interrogators, each interrogator having a plurality ofantenna inputs, each of the plurality of sensing antennas connected toan interrogator, and a computer operatively connected to each of theinterrogators and receiving tag location information therefrom to logtag location data.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, where like numerals refer to like components throughoutthe several views,

FIGS. 1A and 1B are perspective drawings of a dual nesting station witha container having an RFID tag embedded therein;

FIG. 2 is a perspective view of a storage shelf having a plurality ofnesting stations with some tracked container placed thereon;

FIG. 3 is a block diagram view of a system embodiment of the presentinvention;

FIG. 4 is a schematic diagram of an embodiment of a circuit layout for a2×2 pad embodying the invention;

FIG. 5 is diagram of an embodiment of an antenna suitable for use in theembodiment of claim 1;

FIG. 5 a is a top view of another embodiment of an antenna suitable foruse in the embodiment of claim 1;

FIG. 5 b is a section view of the embodiment of FIG. 5 a taken alonglines 5 b—5 b thereof;

FIG. 6 is a circuit diagram of an embodiment of a tuned circuitaccording to the invention;

FIG. 7 is a block schematic diagram of an embodiment of an interrogatorof the present invention;

FIG. 7 a is a schematic diagram of an RF harmonic reduction embodimentof the driver system;

FIG. 8 is a block diagram of another embodiment of an interrogatorsystem of the present invention;

FIG. 9 is a block diagram of another system embodiment of the presentinvention;

FIG. 10 is a side elevation view of an another antenna embodiment of thepresent invention;

FIG. 11 is a flow chart diagram of a method embodiment of the presentinvention;

FIG. 12 is a flow chart diagram of another method embodiment of thepresent invention;

FIG. 13 is a flow chart diagram of a lot association method of thepresent invention;

FIG. 13 a is a flow chart diagram of another method of the presentinvention;

FIG. 14 is a flow chart diagram of an embodiment of a tag attachmentmethod of the present invention;

FIG. 15 is a perspective diagram of a computer system on which variousembodiments of the present invention may be implemented; and

FIG. 16 is a schematic diagram of annunciator embodiments of the presentinvention.

FIG. 17 is a block diagram of another embodiment of an application forthe present invention.

DESCRIPTION OF EMBODIMENTS

In the following detailed description of the embodiments, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown by way of illustration specific embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized and structural changes may be made withoutdeparting from the scope of the present invention.

The physical similarities between inventory operations and other similaroperations such as warehousing, quantity and position tracking, and thelike allow the discussion of one such operation to generalize for anumber of similar operations. As such, this description will discussgenerally a variety of inventory strategies, with the understanding thatgeneralization to other operations may easily be accomplished by one ofordinary skill in the art. Such modification and specification aretherefore within the scope of the present invention.

Physical Overview

An implementation of a portion of a container tracking andidentification system according to the present invention is shown inFIGS. 1A, 1B and 2. Referring to FIG. 1, a dual nesting station 10 isshown upon which an item or container 12 may be placed. Hereafter,reference to container will mean any item which may be tracked by thepresent invention. The dual nesting station contains two locations 14,16 where containers may be placed and tracked according to the presentinvention. A dual nesting station 10 is shown as an exemplaryembodiment, however, those skilled in the art will readily recognizethat a single nesting station 14 may be implemented, or any plurality ofnesting stations may be implemented in accordance with the teachings ofthe present invention. The nesting stations 14, 16 may be implemented asa generally flat component which may be placed wherever there is a needto track a container, or it may be formed as an integral part of ashelf, pallet, bench, table, or any other location where items orcontainers are located.

Each nesting station includes an antenna 18 imbedded within of upon eachnesting stations 14, 16. Other circuitry, not shown in FIGS. 1A and 1Bbut described below, is used to send and receive signals to and from anRFID tag 19 imbedded within or placed upon container 12. As shown inFIG. 1A, when container 12 is placed in proximity to nesting station 14,communication of signals between container RFID tag 19 and antenna 18 ispossible. These communication signals will be more fully describedbelow.

FIG. 2 shows an exemplary implementation of a shelf arrangement 20 withwhich the present invention may be used. A plurality of nesting stations16 are part of the shelf arrangement with each nesting station 16 havingan integral antenna 18 for each shelf location. Containers 12 or otheritems to be tracked, can be placed at various shelf locations and thecontainers 12 can be located, identified, tracked, etc., with theteaching of the present invention. An optional feature of the presentinvention are the use of annunciators or indicators 22 which may be usedto indicate the location of a desired container. Nesting stations 16 maybe placed upon the shelves or they may be integrated with the shelfitself.

System Overview

Referring now to FIG. 3, an embodiment 100 of a system of the presentinvention is shown in block diagram. Lot tracking system 100 comprises ahost or control module 102 operatively connected to a plurality ofinterrogators 104, 106, and 108. The interrogators 104, 106, and 108each have a plurality of sensing antennas and circuitry 110 operativelyconnected to the main interrogator body by connection lines. Theinterrogators 104, 106, 108, are preferably local to the sensing antennacircuits 110. The sensing antenna circuits 110 are positioned so thatthey are in sensing proximity to a location at or over which a pluralityof containers may be located or pass. Each container (shown in FIGS. 1A,1B and 2) is capable of holding items such as lots of wafers used tomanufacture integrated circuits. In such an application of the presentinvention, the container is termed a “boat” and would hold lots ofpartially fabricated or fully fabricated wafers which may be routedthrough the plurality steps required in the IC fabrication at an ICfoundry.

Each container has an attached Radio Frequency IDentification (RFID) tag19 (shown in FIGS. 1A, 1B and 2) capable of being excited by the sensingantenna circuits 110, capable of relaying, conveying, or communicatingidentification information to the sensing antenna circuits, and on tothe control module 102.

The tags are preferably low frequency passive RFID tags 19 which carry aserial number or identification number which can be cross-referencedwithin a database or other data structure maintained by the controlmodule 102 or one of its components. Each interrogator 104, 106, and 108contains drive electronics and detection circuitry to excite and readback identification information contained on a tag. Driving informationis communicated to the tag through the antenna coil or primary of anelectromagnetically coupled circuit. The data out on the communicationline 114, 126, 140 is linkable to the host or control module system forother action. Tags are polled by exciting the sensing antenna circuits110, which induces a current in the tag 19, causing it to communicateits stored information, which will be described in more detail below.

The RFID tags 19 contain generally simple information, but the taginformation may be as widely varied as the uses for the system 100itself. For example, tags can contain simple presence/no presence bit,or detailed information regarding an entire build process, orspecifications about lot number, serial number, and the like. The radiofrequency of the interrogator powers up the tag, and the carrierfrequency (usually 125 KHZ for passive tags in one embodiment) becomesthe clocking frequency to generate a clock to clock the data out.Passive tags can be made and used very inexpensively, making them moreeconomical for use with multiple read locations.

In one arrangement shown in FIG. 3, interrogator 104 is operativelyconnected to a plurality of sensing antenna circuits 110 on a nestingstation 112 via connection lines 114. In this arrangement, twoquad-nesting stations are shown. In another arrangement, interrogator106 is operatively connected to a plurality of sensing antenna circuits116 on quad nesting station 118 via connection line 120, and to antennas122 of dual nesting station 124 via connection line 126. In yet anotherarrangement, interrogator 108 is operatively connected to a plurality ofantenna circuits 128 on a dual nesting station 130 via connection line132, and to antenna circuits 134 on another dual nesting station 136 viaconnection line 138. Further interrogators may be added to theembodiment 100 to accommodate more nesting stations.

Control module 102 may include such components as a computer with adatabase of information pertaining to lot numbers, lot locations, andother lot information for the items in container 12. Control module 102controls the interrogators 104, 106, 108 to poll appropriate locationsto gather and maintain information about containers 12.

The connection lines of embodiment 100 may comprise a plurality of typesof connections such as standard flat phone cables with a phone jackconnector to attach to multiple sensing antennas. Depending upon theconfiguration of the nesting station to which the connection lines areconnected, the telephone cables used in embodiment 100 may be fourconductor flat phone cables, eight conductor flat phone cables, or acombination of such cables. The connector phone jack may be an RJ-11type four conductor jack, or an RJ-45 type eight conductor jack,depending upon the type of cable connection. Flat telephone cable isused so that the drive signals for the antenna circuits (describedbelow) are physically separated from the sense line and are readilyavailable at low cost.

Alternatively, twisted pair cabling may be used in a networkenvironment. In such a configuration, the detection and ground wires(described below) would be twisted together, and the drive signal lineswould be twisted together. Only one drive wire is active at any onetime. One antenna circuit 110 is driven at a time, and a commondetection circuit is used for all of the antennas. The drive signal isswitched from one antenna circuit to the next using a multiplexor (MUX).The switching may be sequential, ordered, or random, but only oneantenna circuit 110 is driven at any one given time. This allows the useof a common detection processor detection circuit which is used for eachantenna circuit of the plurality of antenna circuits that are wired intoeach interrogator. The multiplexor selects which antenna circuit isbeing driven by the drive signal.

The jacks for the connection can be standard telephone connection jacks,selected for their availability and low cost. Those skilled in the artwill readily recognize that a wide variety of wire types, wiringconfigurations and electrical connectors may be used in theimplementation of the present invention without departing from thespirit and scope of the present invention.

Nesting stations have been described above as single-, dual- or quad-,but many other arrangements of nesting stations is possible with thepresent invention. For the example of tracking boxes of semiconductorwafers, each nesting station would be typically implemented as a dualnesting station sized to be approximately one foot by 2 feet to form asuitably sized location for two typical 200 millimeter wafer boxes whichhave a footprint of approximately one square foot. This is referred toas a 1×2 pad. A 2×2 pad would be implemented as a quad nesting stationdescribed above and would be approximately two feet by two feet in size.Thus, a 2×2 would be a quad nesting station for four semiconductor waferboxes.

For a 1×2 pad nesting station such as nesting station 124, 130, or 136,an RJ-11 four conductor jack may be used to connect the four conductortelephone cables 126, 132, and 138, respectively, to the antennacircuits 122, 128, and 134 respectively. For a 2×2 pad nesting stationsuch as nesting station 112 or 118, an RJ-45 eight conductor jack may beused to connect the eight conductor telephone cable 114 or 120respectively to the antenna circuits 110 or 116.

Alternatively, instead of an eight conductor cable such as cable 114 orcable 120, two four conductor cables can be used side by side in anRJ-45 jack. In this case, the opposite ends of the four conductor cablesmay be fitted with RJ-11 phone jacks for ease of connection. Thisconfiguration is useful for connection of two 1×2 pads such as pads 130and 136 to a single interrogator such as interrogator 108. For example,in FIG. 3, cables 132 and 138 may be four conductor telephone cables,each having an RJ-11 jack for connection of the cables to the nestingstations 130 and 136. The two cables 132 and 138 plug into a singleRJ-45 eight position jack to connect the cables to interrogator 108.When two four connector cables are used in a single RJ-45 eightconductor jack, they are mirrored so as to place the detector circuit,that is the signal that has been rectified and has the greatest noisesensitivity, on the outside of the cable where it is furthest from thedrive electronics.

Nesting Pad Description

FIG. 4 shows an exemplary embodiment of a 2×2 pad 152 implemented withtwo 1×2 pads 154 and 156, along with the antenna circuitry, arranged ina mirrored configuration (discussed below) in schematic diagram form. Aconnection 158 for cabling to the interrogator has eight contactpositions 160 which may comprise two four conductor RJ-11 jacks, or asingle eight conductor RJ-45 jack as described above. Each 1×2 pad 154and 156 has a four conductor RJ-11 jack connecting its four contactpositions, 162 and 164 respectively, to an appropriate four conductorcable to the interrogator. As shown, the physical layout of contactpositions 162 mirrors that of the physical layout of contact 164, withposition 162-4 and position 164-4 being adjacent within the 2×2 pad 152.This mirrored configuration places the detection circuit, that is therectified signal with the greatest noise sensitivity, on the outside ofthe cable. The detector conductors (position 1) are therefore placedaway from the drive signal conductors (positions 3,4) by the groundconductors (position 2) to help eliminate noise.

The antennas used in embodiment 100 preferably each comprise a flatcoil, a flat radial single layer antennas comprising a length of copperwire which is coiled to form an antenna. The flat coil constructionallows some degree of side to side movement of the antenna withoutsignificant degradation of performance. Further, the flat coil antennaconstruction also provides relatively good height detection of theantenna without drastically affecting the performance of the system. Aflat coil is less sensitive to surrounding metal surfaces in the sameplane as the coil. Other antennas could also be used. Representativeembodiments of antennas will be discussed further below.

Antenna Circuit Description

FIG. 5 shows a top view of a representative embodiment of a flat antennacoil 200 is shown in FIG. 5. Antenna coil 200 comprises a length ofcoiled wire 202, such as copper wire. Although copper wire is preferred,other conductive wires and embodiments are well within the scope of theinvention, as will be known by one of skill in the art.

FIG. 5 a shows a top view of another embodiment 250 of an antenna.Antenna 250 comprises a substantially circular magnetic core 252 havingan annular ring 254 extending from the core 252 to form a magnetic cup.A magnetic center post 256 extends from the core 252 approximately atthe center of core 252, in the same direction as the annular ring 254.Coil windings 258 are wrapped around the center post 256. FIG. 5 b showsa section view of antenna 250 taken along lines 5 b—5 b of FIG. 5 a.FIG. 5 b shows focused flux lines 260 from the focused antenna 250.

As shown in FIG. 6, each antenna circuit 300 form a tuned tank circuitwhich is connected to interrogators 104, 106, and 108. The interrogatorscontain circuitry for excitation of the tuned tank circuits and fordetection of the information transmitted by an excited RFID tag. Sincethe nesting stations are somewhat remote from the interrogators, thetuned circuit embodiment 300 of the present invention places a capacitor302 in close proximity to the antenna coil 304, so that the entire tankcircuit 300 is remote. Therefore the cable length and type can vary orbe changed without affecting the operation of the antenna 304 and driveelectronics.

One skilled in the art will recognize that if the capacitive element andthe antenna coil were separated, with the capacitive element located atan interrogator would require that the interrogator be part of the tunedcircuit. Cabling between the antenna (nesting station) and thecapacitive element (interrogator) would be a factor in decipheringinformation from any excited tag. In such a configuration, when thelocation of the antenna changed, the tuning of the circuit changed. Thislatter configuration would be problematic since tuning the tank circuitfor proper operation would be time consuming. By placing the entire tankcircuit in the nesting station, the components of the system are readilyinterchangeable and cabling lengths are not a factor in the properoperation.

In operation, the interrogator drives the tuned tank circuit comprisedof series connected elements 302 and 304 with a square wave powersignal. In an exemplary embodiment, the drive signal operates at 125kHz, capacitor 302 is 3000 picoFarads and antenna coil 18, 202, or 304is 800 microHenrys. The square wave drive signal is smoothed to a nearlysine wave signal which is emitted from the antenna coil 304 to exciteRFID tag 19. The excited tag emits a signal containing informationunique to the tag (such as a serial number). This signal from the tag isdetected by antenna coil 304, rectified by diode 306 and sent to theinterrogator for demodulation. The diode 306 generates a rectified peakvoltage of the tank circuit 300 and the detected signal appears as apulse stream in the form of a series of dips in the 125 kHz rectifiedcarrier signal. This pulse stream is then decoded by the interrogatorfor the data it carries.

Interrogator Description

An embodiment 400 of an interrogator is shown in FIG. 7 which includes aprocessor 405 and an antenna reader circuit 404. Antennas areconnectable to the interrogator 400 at connection point 406, andconnection to the power supply and host or control module is effected atpoint 408. Power for operating the interrogator 400 may be obtainedlocally or it may be received through the host communication cable.Communication of processor 405 with host or control module 102 isaccomplished through port 410. Host protocol interface port 410 may be aserial communication RS-232 port, or a differential port such as amulti-drop IEEE 485 or non multi-drop IEEE 422. The host or controlmodule processes instructions according to a predefined operationalstructure, issuing commands to the interrogator for control ofmultiplexor 412 which selects the antenna which is to be driven at anygiven time.

In the exemplary embodiment shown in FIG. 7, each antenna connected tothe interrogator 400 has a dedicated power driver 411 circuit togenerate the square wave excitation signal. The preferred power driverfor the antennas is a low cost CMOS power driver to drive the squarewave which is converted to a sine wave by the tuned circuit. In thisexample, each antenna has its own power driver within the interrogatorbecause an electronic multiplexor switch with a low on resistance wouldbe more expensive than the CMOS drivers. It is desirable to use powerdrivers with fast rise times, such as MOSFET and CMOS power drivers.

Details of the power driver circuitry are shown in FIG. 7 a. Drivers 411have a fast rise time and radiate a high frequency harmonic because ofthat. To slow the rise time, drivers 411 are each connected to theantenna drive voltage through an inductor 413. Further, an inductor 415is electrically interposed between each driver 411 and ground. Theinductors 413 and 415 are used to slow the rises and fall times of thedriver 411 to reduce harmonic radiated RF.

Once the sensing antennas have excited a tag, the information receivedfrom tank circuit such as circuit 300 is sent to interrogator 400 anddetected by detector 414 along a sense line 419. Since only one antennais excited at a time, all detector sense lines 419 from all nestingstations may be wired to the same detector. Processor or microchipcontroller 405 decodes data from the detector circuit 414 and canprovide for sequential, ordered, or random scanning of the ports of thesystem through antenna selector 412.

Detector circuit 414 is preferably implemented with analogamplification/detection of the DC rectified signal of the diode of thetuned circuit. The detected signal can be provided to processor 405where each detection circuit 414 also has decoding capabilities, such asdigital signal processing (DSP) type decoding built in. Each multiplexorboard could have its own detector and processor, allowing for thedriving of multiple antennas at once.

The processor 405 of interrogator 400 can be essentially amicrocomputer, that is an all in one chip with on board RAM, EPROM, I/Opoints, a microprocessor, and analog input. The processor 405 could havehard-coded (burned into PROM) control software, or it could download thecontrol software from a separate processor or computer system.

The interrogator 400 is preferably positioned in close proximity to thesensing antenna, which reduces the bundle of wires that must be run fromthe interrogator to the host computer or control module. From theinterrogator, a low cost serial port may be used to run power into theinterrogator along a communication line from the host. This allows for awide operating voltage, which is preferably maintained low (24V forexample) for safety purposes, but high enough that there is a lowcurrent draw. In this exemplary implementation, there is only one cablewhich needs to be disconnected in the event that the interrogator mustbe moved. In some environments, this a fairly common event. Referringback to FIG. 2, a single interrogator may be located on the shelvingunits and serving all nesting stations of this shelf unit. If the shelfis to be moved, only one cable need be disconnected from the host. Thatcable may be a wall jack with in-the-wall network wires running to thehost.

To keep the efficiency of the system up and power current down, voltageregulation circuitry 416 is used to perform regulation of unregulated24V power to regulated 12V and 5V power. In one embodiment, DC to DCvoltage regulators are used to perform main power reduction from anunregulated 24V power supply to a regulated 12V and 5V power supply todrive the interrogator components.

Alternatively, communications coming through host protocol interface 410could be jumpered to an auxiliary processor board 418 that may containan auxiliary processor 402 and wide variety of optional communication orI/O protocols 421, such as ETHERNET, wireless modem, another processorwith a large amount of memory, or the like. In such a configuration, theentire interrogator system 400 runs without interaction between theinterrogator and the host. Gathered information may be downloaded to thehost or control module at a later time. If no auxiliary processor 402 ispresent, then the connections which would go to the COM and COM1 portsof the auxiliary processor 402 are jumpered together.

A wide variety of auxiliary functions could also be performed by such anauxiliary control I/O 421 piggybacked to the circuit 404. Adaughterboard 418 with auxiliary input/output capability could be usedto unlock doors, generate alarm signals, including local alarm signalsfor an object removed from a nesting station or boat, or the locationfrom which an object has been removed, or drive an operator interfacedisplay terminal.

An interrogator system embodiment 500 of the present invention as shownin FIG. 8 comprises tags 502 and an interrogator 504. Each tag 502 isassociated with a specific lot, and contains identification informationspecific to the lot or item to which the tag is attached. Each tag 502may be attached to a lot box or the like. Each tag, when excited, willcommunicate a signal indicative of its identification information. Thetag can carry such information as a serial number and the like, whichmay be cross-referenced in a database maintained at the system host(computer). Antennas 506 are positioned in close proximity to the lotlocation which they will be polling. Interrogator 504 is connected toantennas 506 by a communication line 508, which in the example shownwill be a four line conductor. Connection jacks 510 and 512 connect thecommunication line 508 to the interrogator 504 and the nesting station506 respectively. As discussed above, a four line conductor willtypically be terminated with an RJ-11 four conductor jack.

Tags 502, as has been mentioned above, are typically passive tags. Thisreduces the overall tag cost, which is important since a large number oftags may be required in application. The passive tags 502, which allowfor low cost, generally have a short effective operating range. Therange may be on the order of 0 to 15-20 inches, depending upon antennasize. The larger the antenna, the greater the operating range. In oneembodiment, the present invention limits the tag range further,preferably on the order of two (2) inches. Taking advantage of thisshort range allows this embodiment of the present invention to excite atag and obtain its information, while also determining its exactlocation. Further, with simple timing and recordation schemes, it ispossible given the precise nature of multiple antenna locations andclose discrimination between lots to know which part is at which exactlocation at any given time.

Each interrogator has an address stored in interrogator address module417, which may be a volatile or a non-volatile memory. Each antennaconnection has a sub-address.

Each antenna array location has its own unique identificationinformation or address. In this way, the unique address can beprogrammed into the system, so that the physical location is notdetermined by where the antenna array is plugged in, but by what theaddress of the array has been programmed to. Then, under that addresseach antenna point will have its own address, allowing resolution downto each specific individual shelf and position. The system resolvesexactly where each item is. This allows the mapping of a shelf and/or alocation for a graphics display or the like, to locate an item withspecificity. The reduced range of the antennas of this embodiment of thepresent invention allow for such a close up representation of exact itemposition. The range of on the order of two inches allows the reading ofeach tag to a precise location.

For example, in a wafer production fabrication, there may be 1000 lotboxes running production wafers, and 1000 lots of test wafers, plus 500lots of reference type wafers, all at a general location. This resultsin 2500 lot boxes in a physical space. This can represent upwards of5000 locations, because of the open queue space which is needed to movelots through such an operation. A system which works must be low costand distributed to allow for multiple read locations, and inexpensiveread points.

With a large number of locations to be polled, multiple interrogatorswill be required. Each interrogator concentrates multiple antennalocations into one interrogator. Typically in a wafer production line,production shelves are 2×4, or eight lots per shelf. Racks of shelvesmay be stacked six shelves high, and may have 32-56 boats per rack.Typically, the maximum number of boats per rack is 60. With twotelephone cable per shelf, a single location may have 12 eight conductorflat cables running from the location to the interrogator. The benefitsof local interrogators multiply with increased numbers of readlocations.

With an interrogator having 60 antennas, 60 sets of data are collectedand stored internally. At the next polling, only absolute differencesare considered. That is, the delta data is polled. If only one of thesets of data has changed, it is the only set of data transmitted. Thisreduces the amount of data required to be transmitted. A completepolling may be taken at a specified interval or number of scans, in oneembodiment every 100 scans. Further, tag information transmitted may belimited in one embodiment. Some tags contain an amount of user specificinformation that is the same for every tag associated with that user. Ifall tags polled are for a certain customer or user, then certainidentification information need not be transmitted. Also, tags out ofrange of a certain specified parameter can be flagged, or an alarm canbe given.

With 180 interrogators in a room, multiple options are available. First,all interrogators could be local, taking gathered information from itsread locations or bays and sending the information into a switchedmultidrop configuration. This configuration would result in some datathroughput difficulties (long time between individual locationinterrogation), but in a slow changing environment this may not becritical. Problems with such a multidrop configuration is that it placesmore equipment in the field, creating more service locations and anincreased number of locations for things to break down. In oneembodiment, communication drops to each interrogator are all sent backto a communications room in a star configuration which is in turnconnected to the host. However, the scale could be dropped down toindividual or a small number of components together on a power supplydepending on the facility requirements.

Alternatively, an infrared link may be positioned on an interrogator, orlocated remote to an interrogator, and an infrared transceiver pod couldbe positioned on the ceiling of a room, for obtaining by infrared thelocation information gathered by each interrogator. Power would stillneed to be provided to each interrogator, most likely on a cable, butfull data communication links to the host would not be required. Othertechnologies could also be supported, such as cellular phone, pager,wireless modem, solar power, and the like.

FIG. 9 shows an embodiment 600 of another system embodying the presentinvention. Multiplexor 606 has a plurality of connections to singleantennas 608 a, 608 b, . . . 608 n, which are driven by drivers 610 a,610 b, . . . 610 n. A common detector circuit 602 is connected inparallel to each of the drivers 610 a, 610 b, . . . 610 n and tocontroller 604. Controller 604 controls selection of which antenna 608is to be active at any given time.

In embodiments of the invention as described above, the use of a flatcoil antenna has been shown to allow some lateral movement of the boxesto allow for positioning tolerances without significant degradation ofperformance. Further, the flat coil antenna construction also providesrelatively good height detection of the antenna without drasticallyaffecting the performance of the system. A flat coil is more sensitiveto ferrous materials in the vicinity of the coil. However, if the shelfor nesting station upon which tags are placed is composed of a materialsuch as wood, plastic, and the like instead of metal, then a balancebetween separation of the antenna from the shelf and the performance ofthe antenna is not an issue.

If the height or distance of the antenna from the tag increases, thecommunication or readability degrades. As the height or distancedecreases, the tuned circuit becomes detuned. Further, if a ferrousmaterial object such as a wrench, clipboard, or pad is placed on or inclose proximity to the nesting station or antenna, a voltage anomaly dueto the object may show up in the output from the diode of the tunedcircuit, and tag communication may degrade. At that point, it will beevident that the antenna is not sensing a tag, but instead is sensingsomething abnormal. For example, if no voltage is indicated in the tunedcircuit, that could indicate that the antenna is not present, or thatthere is a fault in the circuit.

Changes in antenna performance or surrounding load will change the peakrectified voltage from the diode. This changed peak rectified voltagecan be compared to historical data or absolute values to detect systemfaults or performance degradation.

An embodiment 700 of an antenna which decreases sensitivity to anomaliesis shown in FIG. 10. A ferrous cover plate or metal sheet 702 ispositioned a predetermined distance 706 from the back of the antenna704. The metal sheet or cover 702 serves to magnetically preload thecoil 704. This ferric loading of the coil serves to reduce thesensitivity of the antenna 704 to further surrounding metal. The tunedcircuit, such as tuned circuit 300, is then tuned with the cover ormetal sheet 702 in place. It has been determined that a preferableseparation 706 between the antenna 704 and the plate or sheet 702 isapproximately ⅜ of an inch. However, other distances will also serve topreload the tuned circuit.

Process Flow

A method embodiment 800 of tracking the location of identification tagsas shown in FIG. 11 comprises activating a sensing antenna, which ispart of a tuned circuit, to excite a passive identification tag in block802, determining if a voltage is induced in the sensing antenna in block804, and storing or communicating to the host any induced voltage in thesensing antenna in block 808 if a voltage is induced in the sensingantenna.

An interrogator such as interrogator 400 described in detail above withincluded multiplexing capability controls multiple antennas all attachedto the interrogator, with one antenna being driven at any given time. Adetector circuit in the interrogator serves to detect the signalsreturned from the sensing antenna. The method 800 may further compriseactivating a plurality of further sensing antennas in a predetermined orrandom sequence in block 810, followed by the re-execution of blocks 804and 808 as needed.

The sensing antennas and interrogators described in detail above may beused in a tag identification method such as method 800. One or moreprocessors in the interrogator may be used to not only decode datacoming back from the detector circuit but also to provide sequentialscanning of the ports. Process flow in method 800 allows for eitherscanning all antenna locations or ports regardless of whether anythingis plugged into them. In other words, the sensing antenna, tunedcircuit, and detector circuit determine whether an antenna is pluggedinto a location or not by measuring the voltage generated by therectification of the tank circuit. This voltage is typically a nominalvoltage stable across all antennas.

If no voltage is present in decision block 804, several options forfurther process flow are available, and will be described in detailbelow. If no voltage is present, that may indicate that no antenna ispresent. Alternatively, a lookup table or representation of theconfiguration of the antenna system may indicate that there should be anantenna at a given location. Further, when a tag powers up, it may notcorrectly initialize or communicate information. A reinitialization maybe necessary. If no voltage is present in block 804, an alarm for anantenna failure or other alarm condition, such as antenna degradation orthe like, can be generated. The host system can track antenna voltageand compare historical data to detect problems as discussed above.

A self-testing embodiment of a material tracking system is a part of thepresent invention. A self-testing embodiment 1000 is shown in detail inFIG. 12. Self-testing embodiment 1000 incorporates some of the basicprocess flow of embodiment 800. Embodiment 1000 comprises selecting ascan method from a number of possible scanning methods in block 1002,checking an antenna map or the like to allow skipping of inactiveantennas in block 1004, and activating the selected antenna in block802. If no antenna is supposed to be present, process flow can continuewith the next antenna position. If the antenna voltage for the selectedantenna does not exceed a predetermined lower limit as determined bydecision block 1005, the host is alerted or a local alarm is activatedin block 1020. If the antenna voltage for the selected antenna is abovethe predetermined lower limit as determined by decision block 1005,process flow continues with block 1006.

In block 1006, a timeout timer is reset. The timeout timer counts apredetermined time during which the embodiment 1000 waits for tag datato be read. The embodiment waits for tag data or the timeout limit ofthe timeout timer in block 1008. A determination is made as to whethertag data has been detected in decision block 1010. If tag data has beendetected in block 1010, the data is stored or sent to the host in block808, and the next antenna is selected in block 810. Following that,process flow continues with block 1004.

For each instance in which tag data is not detected, an iteration countis compared against an iteration limit in block 1012. A predeterminedlimit of the number of iterations allowed for detecting tag data is setin the embodiment 1000. This number may be set to depend on a number offactors, including the response time of the tags, the required ordesired response time of the circuit, and the like. Each unsuccessfuldetection of tag data results in an incrementing of the iteration count.If no tag data has been detected in block 1010, the iteration count ischecked against a predetermined iteration limit in decision block 1012.If the iteration count is not above the predetermined limit, theiteration counter is incremented in block 1016, and the antenna driveris cycled off and back on in block 1018. Process flow continues withdecision block 1005. If the iteration count is above the predeterminediteration limit, then “no tag” data is generated in block 1014, andprocess flow continues with block 808. At the selection of the nextantenna, the iteration count is reset.

Typically, a time period of approximately 50 milliseconds is enough todetermine whether a signal will be present. This amounts toapproximately two power cycles. If no tag is sensed, the typical scantime is approximately 0.1 seconds for each scan. In a worst casescenario, an entire shelf of 60 antennas with no tags can be scanned inapproximately six (6) seconds. The fastest read conditions occur whenall active antennas have tags present, and all tags properly power up.

Depending upon required response time, the ratio of read points tointerrogators could be increased. At 60 to 1, scan time for a shelf isapproximately 6 seconds. Increasing the read point to interrogator ratioto 500 to 1 or higher would push scan time to around a minute, which isstill acceptable for numerous inventory functions.

Given the availability of polling a shelf of up to 60 positions inapproximately six seconds, any number of possibilities of trackingprocedures and other inventory control functions may be implemented incomputer software. Currently, bar codes on lots are scanned with theinformation therefrom being stored in a database. The identificationtags are generally molded into a wafer boat or box. Typically, the waferbox remains with the lot for most of the lot life except for a fewtimes, for example, when the boxes are washed, or if the box getscontaminated.

Another embodiment 1100 of the present invention for tracking thecarrier box association to a lot is shown in FIG. 13. A lot is placedwith a box in block 1102, and a bar code label is placed on the box inblock 1104. The box is associated with the tag in block 1106. A databaseentry is made regarding the association in block 1108. This samedatabase is used to record the sampling information generated at variouspolling locations around the plant or location in which a systemembodiment of the present invention is in place.

Yet another embodiment 1110 of the present invention for associating atag with material and manufacturer information is shown in FIG. 13 a.Method 1110 comprises scanning, collecting, or entering manufacturerdata into a database in block 1112, attaching a tag to the raw materialin block 1114, and associating the tag with the manufacturer data inblock 1116. The material is moved to storage in block 1118, transportedin block 1120, and is moved through a production line in block 1122.While in any phase of the process 1110, apparatus embodiments of thepresent invention may be used to track the location of the material. Thematerial is transported again in block 1124, and again stored in block1126. At the completion of the production cycle, the tag is removed inblock 1128, and is disposed of or returned for reprogramming in block1130.

An identification tag may be attached to an object to be tracked bymethod embodiment 1150 shown in FIG. 14. Method 1150 comprises forming ashallow polypropylene cup in block 1152, placing the identification tagin the polypropylene cup in block 1154, welding the identification tagto the polypropylene cup ultrasonically in block 1156, and welding thepolypropylene cup to the object ultrasonically in block 1158.

The database generated from all of the association information of thetags and boxes in a particular database can be sampled to generatehistory information. It is envisioned that such a database will beaccessible at multiple locations around a plant or inventory location.The database can be queried to generate the appropriate information. Thepossibilities are numerous given the present invention embodiments'ability to update information of a box approximately every 6 seconds.Information that could be tracked includes by way of example only, andnot by way of limitation, timing a process, timing a transfer time fromone location to another, tracking missing lots, tracking movement oflots, detecting when a tag is missing, and the like.

Further, the information in the database may be queried, and softwarewritten for managing product flow in a production area, scheduling,tracking, notification of arrival and departure, history, spareequipment inventory, and the like. The nearly real-time gathering ofinformation allows vast flexibility limited only by the capabilities ofthe systems on which the software may be implemented.

The methods shown in FIGS. 11, 12, and 13 may be implemented in variousembodiments in a machine readable medium comprising machine readableinstructions for causing a computer 1200 such as is shown in FIG. 15 toperform the methods. The computer programs run on the central processingunit 1202 out of main memory, and may be transferred to main memory frompermanent storage via disk drive 1204 when stored on removable media orvia a network connection or modem connection when stored outside of thepersonal computer, or via other types of computer or machine readablemedium from which it can be read and utilized.

Such machine readable medium may include software modules and computerprograms. The computer programs comprise multiple modules or objects toperform the methods in FIGS. 11, 12, and 13, or the functions of variousmodules in the apparatuses of FIGS. 3, 7, 8, and 9. The type of computerprogramming languages used to write the code may vary between proceduralcode type languages to object oriented languages. The files or objectsneed not have a one to one correspondence to the modules or method stepsdescribed depending on the desires of the programmer. Further, themethod and apparatus may comprise combinations of software, hardware andfirmware.

The software implementing the various embodiments of the presentinvention may be implemented by computer programs of machine-executableinstructions written in any number of suitable languages and stored onmachine or computer readable media such as disk, diskette, RAM, ROM,EPROM, EEPROM, or other device commonly included in a personal computer.Firmware can be downloaded by the host into the microcontroller or theauxiliary processor for implementing the embodiments of the invention.

Annunciator Design

Given a typical scan time for a shelf of approximately six seconds, afeedback mechanism such as an annunciator, bell, whistle, light, or thelike could be used in a circuit such as circuit 150 shown in FIG. 4,that could be used to locate a lot or a specific part in a lot location.A representation such as a graphical representation of a shelf, could beemployed at a visual display terminal, with the exact location of acertain identified part to be shown on the display, Such representation,due to the close detail allowed by the present invention, wouldfacilitate pinpointing the location of an item or lot for easy retrievalof the part or item.

A coordinate mapping system could be used with graphics on a computerscreen, including a number for elevation of a particular shelf in astack, and a standard position for the shelf, for example an XY schemewith shelf number and position.

An annunciator embodiment 1300 of the present invention is shown in FIG.16. A variety of different annunciator type configurations are shown inFIG. 16. For example, one annunciator embodiment 1302 comprises aresistor 1303 and a light emitting diode 1304 connected in series acrossthe incoming square wave signal. The annunciator embodiment 1302 willlight the LED 1304 when the shelf or lot location to which theannunciator embodiment 1302 is connected is polled.

Another annunciator embodiment 1308 comprises a tuned circuit connectedacross an incoming square wave, the tuned circuit having a differentresonance frequency than the resonance frequency of the tuned circuitused as a sensing antenna. Annunciator embodiment 1308 comprises a tunedLC circuit 1310 and an indicator 1312. Indicator 1312 will becomeactivated when the shelf or lot location to which the annunciatorembodiment 1308 is connected is polled with the alternate frequency.

In another annunciator embodiment 1316, a signaling LED 1318 is shown inreverse polarity. In normal operation, suppose that ground is connectedto positive, and a bipolar driver sends a drive signal to an antenna.Switching the drive circuit or the ground polarity allows a pulsingreverse bias causing LED 1318 to light. In normal connections, with apositive bias on LED 1318, it is not lit. Placing a reverse bias on theannunciator embodiment 1316 causes LED 1318 to light.

In another embodiment, an alphanumeric display 1320 is operativelyconnected across an incoming square wave. The display 1320 can derivepower from the line, or power can be externally provided. When the lineis not used for driving an antenna, the display 1320 is recognized bythe system, and the display may be used to display tag information suchas the tag number, lot number, and the like. Once the tag information isdecoded, the path to the host of the microcontroller could shut off theantenna, and an ASCII signal could be sent on a non-LC frequency. Thedisplay recognizes valid data and displays the data.

Primary application of the embodiments of the present invention are seenin wafer applications. However, multiplexing antennas offers a widevariety of other potential applications such as in large parking lotswhere RFID tags are placed at front or rear bumpers of vehicles, forexample, and antennas are placed at the end of the parking space foridentification of location and identity of vehicles. Other uses for thepresent invention include inventory control systems with large numbersof points to be inventoried but not requiring immediate scanning.Another example is material on a conveyer belt for objects that aremomentarily stationary or stationary within approximately a ten secondor longer period. Such modifications, variations, and other uses will beapparent to one of skill in the art, and are within the scope of thepresent invention.

For example, another embodiment of an application 1700 for the presentinvention is shown in FIG. 17. Tracking of raw material such as gasbottles, chemical bottles such as gas container 1702 is accomplishedusing an omnidirectional tag 1704 situated around the neck of a canister1702 contained in a cabinet or other enclosure 1706. An antenna 1708connected to a system such as those discussed above receives informationfrom collar or tag 1704 upon polling of the tag location. An auxiliaryI/O control such as control 421 is used to actuate a valve 1710 todispense gas from the container 1702. The auxiliary control controls thegas flow, rate of dispensation, and the like.

Manufacture of the Nesting Stations

Physical implementation of the nesting stations may vary. Oneimplementation is to use a clamshell-type plastic molding with moldedridges, stiffeners and anchor points molded directly into the plastic.The circuit board for the tuned tank includes the capacitors with theconnection jacks mounted directly on the circuit board. The circuitboard lays in a notch in the top half of the assembly. The metal groundplane plate is placed in the bottom half of the assembly. The antennacoil leads are attached to the circuit board while the antenna coilwould be attached to the top half of the molding. A foam filler fillsthen fills the void and the molding is closed. The assembly of this typeis key to keeping the cost low. The configurations allowed by this typeof assembly cover very diverse arrangements.

CONCLUSION

The embodiments of the present invention have added multiplexingcircuitry to an interrogator, allowing a single detection circuit andprocessor to be common to a plurality of antennas. A control module orhost is used to control the driving of the antennas.

The embodiments of the present invention take advantage of a short rangeof a sensing antenna to distinguish multiple lots which may be placedvery close together in a small area. One interrogator can distinguishmany items. The invention has a low cost per read station, which isbeneficial due to the large number of read locations.

1. An alert apparatus for an RFID tracking system, the alert apparatuscomprising: a tuned circuit comprising an inductor and a capacitor tunedto a tuned frequency; a resistor; and a light emitting diode connectedin series with the resistor, wherein the series connection of theresistor and the light emitting diode is connected across the tunedcircuit.
 2. The alert apparatus of claim 1, wherein the capacitor has acapacitance of about 3000 picofarads and the inductor has an inductanceof about 800 microhenrys.
 3. The alert apparatus of claim 1, wherein thealert apparatus is connected to a lot location configured to bemonitored by the RFID tracking system.
 4. An alert apparatus for an RFIDtracking system having a tuned circuit, the alert apparatus comprising:a second tuned circuit, connected across the input to the RFID systemtuned circuit, the second tuned circuit tuned to a different frequencythan the RFID system tuned circuit, the second tuned circuit comprising:a capacitor; and an inductor and an indicator connected in parallel, theinductor and indicator parallel connection connected in series with thecapacitor.
 5. The alert apparatus of claim 4, wherein the tuned circuitof the RFID tracking system is an LC circuit with a capacitance of about3000 picofarads and an inductance of about 800 microhenrys.
 6. The alertapparatus of claim 4, wherein the alert apparatus is connected to a lotlocation configured to be monitored by the RFID tracking system.
 7. Analert apparatus for an RFID tracking system, the alert apparatuscomprising: a tuned circuit including a sensing antenna and having atuned frequency; and an alphanumeric display operatively coupled acrossan input to the tuned circuit.
 8. The alert apparatus of claim 7,wherein the tuned frequency is about 125 kHz.
 9. The alert apparatus ofclaim 7, wherein the alert apparatus is connected to a lot locationconfigured to be monitored by the RFID tracking system.
 10. The alertapparatus of claim 7, wherein the alert apparatus further includes apower source for the alphanumeric display, the power source separatefrom the input to the tuned circuit.
 11. The alert apparatus of claim 7,wherein the alphanumeric display is configured to receive an ASCIIsignal at a frequency other than the tuned frequency to display taginformation related to a tag tracked by the sensing antenna.
 12. Analert apparatus for an RFID tracking system having a plurality ofsensing antennas, the alert apparatus comprising: a coordinate mappingsystem coupled to the RFID tracking system; a computer coupled to thecoordinate mapping system, the computer system configured with agraphics display representative of the RFID tracking system to provide avisual indication of a sensing antenna scanning a location identified bythe coordinate mapping system; and a plurality of annunciators, eachannunciator to attach to a nesting station adapted for mounting asensing antenna of the plurality of sensing antenna, wherein eachsensing antenna is configured as an element of a tuned circuit tooperate at a tuned frequency.
 13. The alert apparatus of claim 12,wherein the coordinate mapping system is configured to provide locationinformation of a sensing antenna in response to the RFID tracking systemactivating the sensing antenna.
 14. The alert apparatus of claim 12,wherein the computer is configured to provide a visual indication of asensing antenna scanning a location identified by the coordinate mappingsystem in response to the RFID tracking system activating the sensingantenna.
 15. The alert apparatus of claim 12, wherein the computer isconfigured to display a visual indication of a sensing antenna scanninga location in terms of a stack of shelves and a shelf in the stack ofshelves.
 16. An alert apparatus for an RFID tracking system, the alertapparatus comprising: a tuned circuit including a sensing antenna andhaving a tuned frequency; a resistor; a light emitting diode connectedin series with the resistor, the series connection of the resistor andthe light emitting diode connected across the tuned circuit; a computercoupled to an interrogator of the RFID tracking system, the interrogatordriving the tuned circuit, the computer system configured with agraphics display representative of the RFID tracking system; and acoordinate mapping system operatively coupled to the computer, whereinthe coordinate mapping system is configured to provide locationinformation of the sensing antenna.
 17. The alert apparatus of claim 16,wherein the tuned frequency is about 125 kHz.
 18. The alert apparatus ofclaim 16, wherein the tuned circuit, the resistor, and the lightemitting diode are connected to a lot location configured to bemonitored by the RFID tracking system.
 19. The alert apparatus of claim16, wherein the coordinate mapping system is configured to providelocation information of the sensing antenna in response to the RFIDtracking system activating the sensing antenna.
 20. The alert apparatusof claim 16, wherein the computer is configured to provide a visualindication of the sensing antenna scanning a location identified by thecoordinate mapping system in response to the RFID tracking systemactivating the sensing antenna.
 21. The alert apparatus of claim 16,wherein the computer is configured to display a visual indication of thesensing antenna scanning a location in terms of a stack of shelves and ashelf in the stack of shelves.
 22. An alert apparatus for an RFIDtracking system, the alert apparatus comprising: a second tuned circuitconnected across an input to a tuned circuit of the RFID trackingsystem, the tuned circuit of the RFID tracking system including asensing antenna, the second tuned circuit tuned to a different frequencythan the tuned circuit of the RFID tracking system, the second tunedcircuit including a capacitor and inductor; an indicator connected inseries with the second tuned circuit, the series connection of theindicator and the second tuned circuit connected across the tunedcircuit of the RFID tracking system; a computer coupled to aninterrogator of the RFID tracking system, the interrogator driving thetuned circuit of the RFID tracking system, the computer systemconfigured with a graphics display representative of the RFID trackingsystem; and a coordinate mapping system operatively coupled to thecomputer, wherein the coordinate mapping system is configured to providelocation information of the sensing antenna.
 23. The alert apparatus ofclaim 22, wherein the tuned circuit of the RFID tracking system is an LCcircuit with a capacitance of about 3000 picofarads and an inductance ofabout 800 microhenrys.
 24. The alert apparatus of claim 22, wherein thesecond tuned circuit and the indicator are connected to a lot locationconfigured to be monitored by the RFID tracking system.
 25. The alertapparatus of claim 22, wherein the coordinate mapping system isconfigured to provide location information of the sensing antenna inresponse to the RFID tracking system activating the sensing antenna. 26.The alert apparatus of claim 22, wherein the computer is configured toprovide a visual indication of the sensing antenna scanning a locationidentified by the coordinate mapping system in response to the RFIDtracking system activating the sensing antenna.
 27. The alert apparatusof claim 22, wherein the computer is configured to display a visualindication of the sensing antenna scanning a location in terms of astack of shelves and a shelf in the stack of shelves.
 28. An alertapparatus for an RFID tracking system, the alert apparatus comprising: atuned circuit including a sensing antenna and having a tuned frequency;an alphanumeric display operatively coupled across an input to the tunedcircuit; a computer coupled to an interrogator of the RFID trackingsystem, the interrogator driving the tuned circuit, the computer systemconfigured with a graphics display representative of the RFID trackingsystem; and a coordinate mapping system operatively coupled to thecomputer, wherein the coordinate mapping system is configured to providelocation information of the sensing antenna.
 29. The alert apparatus ofclaim 28, wherein the tuned frequency is about 125 kHz.
 30. The alertapparatus of claim 28, wherein the tuned circuit and the alphanumericdisplay are connected to a lot location configured to be monitored bythe RFID tracking system.
 31. The alert apparatus of claim 28, whereinthe alphanumeric display is configured to receive an ASCII signal at afrequency other than the tuned frequency to display tag informationrelated to a tag tracked by the sensing antenna.
 32. The alert apparatusof claim 28, wherein the coordinate mapping system is configured toprovide location information of the sensing antenna in response to theRFID tracking system activating the sensing antenna.
 33. The alertapparatus of claim 28, wherein the computer is configured to provide avisual indication of the sensing antenna scanning a location identifiedby the coordinate mapping system in response to the RFID tracking systemactivating the sensing antenna.
 34. The alert apparatus of claim 28,wherein the computer is configured to display a visual indication of thesensing antenna scanning a location in terms of a stack of shelves and ashelf in the stack of shelves.
 35. An alert apparatus for an RFIDtracking system, the alert apparatus comprising: a tuned circuitincluding a sensing antenna, the tuned circuit responsive to a signalfrom a bipolar driver circuit; a resistor; and a light emitting diodeconnected in series with the resistor, the series combination of theresistor and the light emitting diode coupled across the tuned circuit,wherein the light emitting diode is configured with reverse polaritywith respect to the tuned circuit.
 36. The alert apparatus of claim 35,wherein the tuned circuit of the RFID tracking system is an LC circuitwith a capacitance of about 3000 picofarads and an inductance of about800 microhenrys.
 37. The alert apparatus of claim 35, wherein the alertapparatus is connected to a lot location configured to be monitored bythe RFID tracking system.
 38. The alert apparatus of claim 35, whereinthe bipolar driver circuit is configured to apply a reverse bias to thelight emitting diode during a scan operation of the sensing antenna.